I’m obviously doing something wrong because I’ve used up a ton of sanding disc. These are great tools but they don’t come with directions on how to use them. Which side of the sander is actually doing the sanding? The center of each disc seems to wear out first, is that the part that sands, and if so what difference does size of sander make then??
I put too much shellac on a maple dresser, now I’m trying to get down to just the top layer without cutting threw the finish itself. I keep seeing the deep scratches. They should disappear as I work through the grits, but I must be using the sander incorrectly. PLEASE Help!!!
How do I know when the disc is all used up and it’s time to change it?
Edited 11/8/2008 12:49 pm ET by shopchallenged
Replies
Hi,
With random orbit sanders, you can use the edge of the disc for feathering in shapes or making some blending cuts with the disc. But you may be pushing down hard on the sander causing the edges to lift a bit and cut more in the center.
It seems counter intuitive, but start sanding with the sander resting on the board and then turn it on. You are seeing sanding scratches now because when the spinning disc hits the wood it's moving fast and it puts those big scratches in. Starting on the wood will leave scratch marks of course but not as big and you can rub those out more easily.
As for sanding through shellac, well good luck. That's a tough job. I'd hit the shellac with denatured alcohol and try pulling up the shellac with a cotton cloth first. You'll be softening the shellac that way with the thinner. You could also try wet sanding with silicon carbide sandpaper wetted down with alcohol to cut through the shellac.
You're also going to be able to see every little scratch as well in a shellac finish. I'd move to hand sanding myself and save the random orbit sanding for when you're down to bare wood again. Good luck.
Gary Rogowski
http://www.northwestwoodworking.com
Thanks Gary
I think I may have pushed down too hard causing the center to drag. I tried the alcohol wipe and ended up with a real mess. I decided to do as you suggested, hand sand. After all the work I've put into this piece I don't want scratches ruining the finish. Next time I'll know enough not to put too much on in the first place.
When I started this project, I hand sanding with a 150 silicone carbide paper, thought I took the finish off. I didn't of course, I should have just kept going down in grit and I wouldn't be where I am now. Instead I wiped on 3 new coats. Didn't get the gloss, so I brushed on 2 really heavy coats on top of the three (+ the 4 I already wiped and sanded). Talk about dumb. Then I took an old Tee shirt dampened it with denatured alcohol and tried to wipe it off. I wiped and wiped, but it just made it a terrible mess. Thus I resorted to the ROS. I may get the rag really wet and try wiping again.
Hi,
Stop work for a second and let's figure this out. If the scratches you have are in your finish, we have a couple of options. You could let the finish cure for a week or two and then sand down to the scratches and remove them. By letting the finish completely cure it will be harder and so easier to sand. Start with 400 grit and see if that works. If it doesn't work, go coarser with your paper. Sand with the grain direction and work the scratches out with as fine a grit as you can. Then sand up to 600 grit or so again and then you can refinish with many light coats of shellac.If the scratches however are in the wood, then you need to get rid of the finish so that you're sanding out the wood. I recommended the alcohol wipe and didn't say use a scraper with it. Because as you discovered, it's a mess. The alcohol will just loosen things up not remove them. Use the alcohol to loosen and scrape the finish off with a scraper. This can be a card scraper or a piece of plastic like a credit card. But it's gonna be messy. I would do an entire surface to make the job simpler and if the edges, for instance, look good, leave them alone. But get rid of the old shellac and get down to the wood and take out the scratches. Good luck. Sometimes it's better to admit defeat and start over, then to try to fix a finish by applying more on top of it.
Best, Gary
Gary
How do I know if the scratches are in the wood under the finish? I sanded the thing down to 220, then wiped it with mineral spirits to see how it would look wet. I didn't see any scratches so I went ahead and applied the finish. So, the scratches could be in the wood not the finish?
I let the shellac cure 3 weeks before I touched it, mostly cause I never got time to get back to it.
The scratches seem to run with the grain and are primarily along joints. Like one side of the joint had softer wood and sanded differently. I'm finding Maple is a tricky wood to master, it's sort of like Poplar. Should I have used a coat of filler across the top like done with Oak or walnut?
Hi,
Yes the sanding scratches could be in the wood. If you didn't sand those out as you moved up through your grits, you could still be seeing them underneath the finish. I would scrape the finish off and resand the top. Do not fill the maple as the pores are so small it will be a waste of effort. I think the problem may have arisen when you scraped or sanded your joints. I'm assuming these are edge joints. Could be you left some deep scratches in there. Here's something that can happen. You will sand your work and it will feel fine running your hand with the grain. But run your hand cross grain and you'll feel lumps and bumps. Always check in several directions to make sure your sanding is even and consistent. Good luck. You'll get it. Gary Rogowski
http://www.northwestwoodworking.com
Gary
Thanks for the help. Just to be sure I'm going back to square on. strip it and resand.
Yes, they are edge joints. I didn't use my card scraper and I should have. Got a tendon problem in my hand and didn't want to make it worse.
Anyhow Thanks again
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